Effect of restricted-feeding strategies on blood concentrations of hormones, metabolites, and minerals in Holstein × Zebu finishing steers

Abstract The objectives were to determine the effects of restricted-feeding strategies on blood concentrations of hormones, metabolites, and minerals in Holstein × Zebu finishing steers. Twenty steers (body weight = 319 ± 16.2 kg; age = 19 ± 1 months) were randomly allotted in 4 groups of 5 steers, which were restricted to 85% ad libitum feed intake for either 0 (R0; n = 5), 28 (R28; n = 5), 42 (R42; n = 5) or 84 (R84; n = 5) days of an 84-d finishing period. Steers were individually housed and considered the experimental unit. Blood samples were collected on d 0, 21, 42, 63, and 84, and were assayed for insulin-like growth factor 1 (IGF-1), thyroid hormones (T3 and T4), albumin, creatinine, urea, total protein, glucose, triglycerides, calcium, and phosphorus. Steers had increasing IGF-1 concentrations until d 42 when restricted-fed. Steers fed R84 had the greatest IGF-1 concentrations on d 84. Urea concentrations were greatest in steers fed R0 and least in steers fed R28; steers fed R42 and R84 were intermediate and not different from one another. Concentrations of IGF-1, urea, albumin, and calcium, but not T3, T4, glucose, triglycerides, creatinine, total protein, and phosphorus were affected by restricted-feeding strategies in Holstein × Zebu finishing steers.

摘要 本研究旨在探讨限饲策略对荷斯坦×瘤牛（Holstein × Zebu）杂交育肥阉牛血液激素、代谢物及矿物质浓度的影响。选取20头体质量为319±16.2 kg、年龄为19±1月龄的阉牛，随机分为4组，每组5头。在为期84 d的育肥周期内，各组分别按自由采食量（ad libitum）的85%进行限饲，限饲时长分别为0 d（R0组，n=5）、28 d（R28组，n=5）、42 d（R42组，n=5）及84 d（R84组，n=5）。所有阉牛均单栏饲养，以个体作为实验单位。分别于第0、21、42、63及84天采集血液样本，检测胰岛素样生长因子1（insulin-like growth factor 1, IGF-1）、甲状腺激素（T3、T4）、白蛋白、肌酐、尿素、总蛋白、葡萄糖、甘油三酯、钙及磷的浓度。限饲阉牛的IGF-1浓度在限饲阶段持续上升，直至第42天；R84组阉牛在第84天时的IGF-1浓度最高。R0组阉牛的尿素浓度最高，R28组最低，R42组与R84组的尿素浓度处于中间水平且组间无显著差异。荷斯坦×瘤牛杂交育肥阉牛的IGF-1、尿素、白蛋白及钙浓度受限饲策略的显著影响，而T3、T4、葡萄糖、甘油三酯、肌酐、总蛋白及磷浓度则不受其影响。